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Meanti R, Bresciani E, Rizzi L, Coco S, Zambelli V, Dimitroulas A, Molteni L, Omeljaniuk RJ, Locatelli V, Torsello A. Potential Applications for Growth Hormone Secretagogues Treatment of Amyotrophic Lateral Sclerosis. Curr Neuropharmacol 2023; 21:2376-2394. [PMID: 36111771 PMCID: PMC10616926 DOI: 10.2174/1570159x20666220915103613] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Revised: 07/18/2022] [Accepted: 08/01/2022] [Indexed: 11/22/2022] Open
Abstract
Amyotrophic lateral sclerosis (ALS) arises from neuronal death due to complex interactions of genetic, molecular, and environmental factors. Currently, only two drugs, riluzole and edaravone, have been approved to slow the progression of this disease. However, ghrelin and other ligands of the GHS-R1a receptor have demonstrated interesting neuroprotective activities that could be exploited in this pathology. Ghrelin, a 28-amino acid hormone, primarily synthesized and secreted by oxyntic cells in the stomach wall, binds to the pituitary GHS-R1a and stimulates GH secretion; in addition, ghrelin is endowed with multiple extra endocrine bioactivities. Native ghrelin requires esterification with octanoic acid for binding to the GHS-R1a receptor; however, this esterified form is very labile and represents less than 10% of circulating ghrelin. A large number of synthetic compounds, the growth hormone secretagogues (GHS) encompassing short peptides, peptoids, and non-peptidic moieties, are capable of mimicking several biological activities of ghrelin, including stimulation of GH release, appetite, and elevation of blood IGF-I levels. GHS have demonstrated neuroprotective and anticonvulsant effects in experimental models of pathologies both in vitro and in vivo. To illustrate, some GHS, currently under evaluation by regulatory agencies for the treatment of human cachexia, have a good safety profile and are safe for human use. Collectively, evidence suggests that ghrelin and cognate GHS may constitute potential therapies for ALS.
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Affiliation(s)
- Ramona Meanti
- School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, Monza, 20900, Italy
| | - Elena Bresciani
- School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, Monza, 20900, Italy
| | - Laura Rizzi
- School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, Monza, 20900, Italy
| | - Silvia Coco
- School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, Monza, 20900, Italy
| | - Vanessa Zambelli
- School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, Monza, 20900, Italy
| | - Anna Dimitroulas
- Faculty of Health and Medical Sciences, University of Surrey, Stag Hill, Guildford, GU2 7XH, United Kingdom
| | - Laura Molteni
- School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, Monza, 20900, Italy
| | - Robert J. Omeljaniuk
- Department of Biology, Lakehead University, 955 Oliver Rd, Thunder Bay, Ontario, P7B 5E1, Canada
| | - Vittorio Locatelli
- School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, Monza, 20900, Italy
| | - Antonio Torsello
- School of Medicine and Surgery, University of Milano-Bicocca, Via Cadore 48, Monza, 20900, Italy
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Ringuet MT, Furness JB, Furness SGB. G protein-coupled receptor interactions and modification of signalling involving the ghrelin receptor, GHSR1a. J Neuroendocrinol 2022; 34:e13077. [PMID: 34931385 DOI: 10.1111/jne.13077] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Accepted: 12/05/2021] [Indexed: 12/28/2022]
Abstract
The growth hormone secretagogue receptor 1a (GHSR1a) is intriguing because of its potential as a therapeutic target and its diverse molecular interactions. Initial studies of the receptor focused on the potential therapeutic ability for growth hormone (GH) release to reduce wasting in aging individuals, as well as food intake regulation for treatment of cachexia. Known roles of GHSR1a now extend to regulation of neurogenesis, learning and memory, gastrointestinal motility, glucose/lipid metabolism, the cardiovascular system, neuronal protection, motivational salience, and hedonic feeding. Ghrelin, the endogenous agonist of GHSR1a, is primarily located in the stomach and is absent from the central nervous system (CNS), including the spinal cord. However, ghrelin in the circulation does have access to a small number of CNS sites, including the arcuate nucleus, which is important in feeding control. At some sites, such as at somatotrophs, GHSR1a has high constitutive activity. Typically, ghrelin-dependent and constitutive GHSR1a activation occurs via Gαq/11 pathways. In vitro and in vivo data suggest that GHSR1a heterodimerises with multiple G protein-coupled receptors (GPCRs), including dopamine D1 and D2, serotonin 2C, orexin, oxytocin and melanocortin 3 receptors (MCR3), as well as the MCR3 accessory protein, MRAP2, providing possible mechanisms for its many physiological effects. In all cases, the receptor interaction changes downstream signalling and the responses to receptor agonists. This review discusses the signalling mechanisms of GHSR1a alone and in combination with other GPCRs, and explores the physiological consequences of GHSR1a coupling with other GPCRs.
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Affiliation(s)
- Mitchell Ty Ringuet
- Department of Anatomy and Physiology, University of Melbourne, Parkville, VIC, Australia
| | - John Barton Furness
- Department of Anatomy and Physiology, University of Melbourne, Parkville, VIC, Australia
- Florey Institute of Neuroscience and Mental Health, Parkville, VIC, Australia
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Abstract
Ghrelin is a peptide hormone secreted primarily by the stomach that acts upon the growth hormone secretagogue receptor (GHSR1), a G protein-coupled receptor whose functions include growth hormone secretion, appetite regulation, energy expenditure, regulation of adiposity, and insulin release. Following the discovery that GHSR1a stimulates food intake, receptor antagonists were developed as potential therapies to regulate appetite. However, despite reductions in signalling, the desired effects on appetite were absent. Studies in the past 15 years have demonstrated GHSR1a can interact with other transmembrane proteins, either by direct binding (i.e. heteromerisation) or via signalling cross-talk. These interactions have various effects on GHSR1a signalling including preferential coupling to one pathway (i.e. biased signalling), coupling to a unique G protein (G protein switching), suppression of GHSR1a signalling, and enhancement of signalling by both receptors. While many of these interactions have been shown in cells overexpressing the proteins of interest and remain to be verified in tissues, substantial evidence exists showing that GHSR1a and the dopamine receptor D1 (DRD1) form heteromers, which promote synaptic plasticity and formation of hippocampal memory. Additionally, a reduction in GHSR1a-DRD1 complexes in favour of establishment of GHSR1a-Aβ complexes correlates with Alzheimer's disease, indicating that GHSR1a heteromers may have pathological functions. Herein, we summarise the evidence published to date describing interactions between GHSR1a and transmembrane proteins, discuss the experimental strengths and limitations of these studies, describe the physiological evidence for each interaction, and address their potential as novel drug targets for appetite regulation, Alzheimer's disease, insulin secretion, and inflammation.
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Affiliation(s)
- Maria L Price
- Institute of Metabolism and Systems Research and Centre for Endocrinology, Diabetes and Metabolism, University of Birmingham, Birmingham, UK
- Centre of Membrane Proteins and Receptors (COMPARE), Universities of Birmingham and Nottingham, Birmingham, UK
| | - Cameron D Ley
- Institute of Metabolism and Systems Research and Centre for Endocrinology, Diabetes and Metabolism, University of Birmingham, Birmingham, UK
- Centre of Membrane Proteins and Receptors (COMPARE), Universities of Birmingham and Nottingham, Birmingham, UK
| | - Caroline M Gorvin
- Institute of Metabolism and Systems Research and Centre for Endocrinology, Diabetes and Metabolism, University of Birmingham, Birmingham, UK
- Centre of Membrane Proteins and Receptors (COMPARE), Universities of Birmingham and Nottingham, Birmingham, UK
- Correspondence should be addressed to C M Gorvin:
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Silver Z, Abbott-Tate S, Hyland L, Sherratt F, Woodside B, Abizaid A. Ghrelin receptor signaling is not required for glucocorticoid-induced obesity in female mice. J Endocrinol 2021; 250:37-48. [PMID: 34060474 DOI: 10.1530/joe-20-0579] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Accepted: 06/01/2021] [Indexed: 11/08/2022]
Abstract
Chronic exposure to high circulating glucocorticoid or ghrelin concentrations increases food intake, weight gain and adiposity, suggesting that ghrelin could contribute to the metabolic effects of chronic glucocorticoids. In male mice, however, blocking ghrelin receptor (GHSR) signaling increased the weight gain and adiposity induced by chronic corticosterone (CORT), rather than attenuating them. In the current study, we investigated the role of GHSR signaling in the metabolic effects of chronic exposure to high circulating CORT in female mice. To do this, female WT and GHSR KO mice were treated with either CORT in a 1% ethanol (EtOH) solution or 1% EtOH alone in their drinking water for 32 days (n = 5-8/group). Body weight, food, and water intake as well as vaginal cyclicity were assessed daily. As expected, CORT treatment-induced significant increases in body weight, food intake, adiposity and also impaired glucose tolerance. In contrast to results observed in male mice, WT and GHSR KO female mice did not differ on any of these parameters. Neither plasma levels of ghrelin, LEAP-2, the endogenous GHSR antagonist produced by the liver, nor their ratio were altered by chronic glucocorticoid exposure. In addition, CORT treatment disrupted vaginal cyclicity, produced a reduction in sucrose consumption and increased locomotor activity regardless of genotype. Chronic CORT also decreased exploration in WT but not GHSR KO mice. Collectively, these data suggest that most metabolic, endocrine, reproductive and behavioral effects of chronic CORT exposure are independent of GHSR signaling in female mice.
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Affiliation(s)
- Zachary Silver
- Department of Neuroscience, Carleton University, Ottawa, Ontario, Canada
| | - Sam Abbott-Tate
- Department of Neuroscience, Carleton University, Ottawa, Ontario, Canada
| | - Lindsay Hyland
- Department of Neuroscience, Carleton University, Ottawa, Ontario, Canada
| | - Frances Sherratt
- Department of Neuroscience, Carleton University, Ottawa, Ontario, Canada
| | - Barbara Woodside
- Department of Neuroscience, Carleton University, Ottawa, Ontario, Canada
| | - Alfonso Abizaid
- Department of Neuroscience, Carleton University, Ottawa, Ontario, Canada
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Cornejo MP, Castrogiovanni D, Schiöth HB, Reynaldo M, Marie J, Fehrentz JA, Perello M. Growth hormone secretagogue receptor signalling affects high-fat intake independently of plasma levels of ghrelin and LEAP2, in a 4-day binge eating model. J Neuroendocrinol 2019; 31:e12785. [PMID: 31469195 DOI: 10.1111/jne.12785] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Revised: 08/16/2019] [Accepted: 08/27/2019] [Indexed: 12/25/2022]
Abstract
The growth hormone secretagogue receptor (GHSR) is a G protein-coupled receptor that is highly expressed in the central nervous system. GHSR acts as a receptor for ghrelin and for liver-expressed antimicrobial peptide 2 (LEAP2), which blocks ghrelin-evoked activity. GHSR also displays ligand-independent activity, including a high constitutive activity that signals in the absence of ghrelin and is reduced by LEAP2. GHSR activity modulates a variety of food intake-related behaviours, including binge eating. Previously, we reported that GHSR-deficient mice daily and time-limited exposed to a high-fat (HF) diet display an attenuated binge-like HF intake compared to wild-type mice. In the present study, we aimed to determine whether ligand-independent GHSR activity affects binge-like HF intake in a 4-day binge-like eating protocol. We found that plasma levels of ghrelin and LEAP2 were not modified in mice exposed to this binge-like eating protocol. Moreover, systemic administration of ghrelin or LEAP2 did not alter HF intake in our experimental conditions. Interestingly, we found that central administration of LEAP2 or K-(D-1-Nal)-FwLL-NH2 , which are both blockers of constitutive GHSR activity, reduced binge-like HF intake, whereas central administration of ghrelin or the ghrelin-evoked GHSR activity blockers [D-Lys3]-GHRP-6 and JMV2959 did not modify binge-like HF intake. Taken together, current data indicate that GHSR activity in the brain affects binge-like HF intake in mice independently of plasma levels of ghrelin and LEAP2.
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Affiliation(s)
- María Paula Cornejo
- Laboratory of Neurophysiology of the Multidisciplinary Institute of Cell Biology, IMBICE, Argentine Research Council (CONICET) and Scientific Research Commission, Province of Buenos Aires (CIC-PBA), National University of La Plata, La Plata, Argentina
| | - Daniel Castrogiovanni
- Laboratory of Neurophysiology of the Multidisciplinary Institute of Cell Biology, IMBICE, Argentine Research Council (CONICET) and Scientific Research Commission, Province of Buenos Aires (CIC-PBA), National University of La Plata, La Plata, Argentina
| | - Helgi B Schiöth
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Uppsala, Sweden
- Institute for Translational Medicine and Biotechnology, Sechenov First Moscow State Medical University, Moscow, Russia
| | - Mirta Reynaldo
- Laboratory of Neurophysiology of the Multidisciplinary Institute of Cell Biology, IMBICE, Argentine Research Council (CONICET) and Scientific Research Commission, Province of Buenos Aires (CIC-PBA), National University of La Plata, La Plata, Argentina
| | - Jacky Marie
- Faculté de Pharmacie, Institut des Biomolécules Max Mousseron, UMR 5247 CNRS-Université Montpellier-ENSCM, Montpellier, France
| | - Jean-Alain Fehrentz
- Faculté de Pharmacie, Institut des Biomolécules Max Mousseron, UMR 5247 CNRS-Université Montpellier-ENSCM, Montpellier, France
| | - Mario Perello
- Laboratory of Neurophysiology of the Multidisciplinary Institute of Cell Biology, IMBICE, Argentine Research Council (CONICET) and Scientific Research Commission, Province of Buenos Aires (CIC-PBA), National University of La Plata, La Plata, Argentina
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Zallar LJ, Beurmann S, Tunstall BJ, Fraser CM, Koob GF, Vendruscolo LF, Leggio L. Ghrelin receptor deletion reduces binge-like alcohol drinking in rats. J Neuroendocrinol 2019; 31:e12663. [PMID: 30456835 DOI: 10.1111/jne.12663] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 10/07/2018] [Accepted: 11/15/2018] [Indexed: 12/13/2022]
Abstract
Ghrelin is a gastric hormone that has been implicated in the neurobiology of alcohol drinking. We have recently developed a ghrelin receptor (growth hormone secretagogue receptor; GHSR) knockout (KO) rat model, which exhibits reduced food consumption and body weight. In addition, recent preliminary work suggests that the gut-microbiome, which appears to interact with the ghrelin system, may modulate alcohol drinking. In the present study, we investigated the effects of GHSR deletion on alcohol consumption utilising GHSR KO and wild-type (WT) rats in three separate alcohol consumption paradigms: (i) operant self-administration (30-minute sessions); (ii) drinking in the dark (DID) (4-hour sessions); and (iii) intermittent access (24-hour sessions). These paradigms model varying degrees of alcohol consumption. Furthermore, we aimed to investigate the gut-microbiome composition of GHSR KO and WT rats before and after alcohol exposure. We found that the GHSR KO rats self-administered significantly less alcohol compared to WT rats in the operant paradigm, and consumed less alcohol than WT in the initial stages of the DID paradigm. No genotype differences were found in the intermittent access test. In addition, we found a significant decrease in gut-microbial diversity after alcohol exposure in both genotypes. Thus, the present results indicate that the ghrelin system may be involved in drinking patterns that result in presumably increased alcohol exposure levels. Furthermore, GHSR may constitute a potential pharmacological target for the reduction of binge-alcohol consumption. The potential functional role of the gut-microbiome in alcohol drinking, as well as interaction with the ghrelin system, is an interesting topic for further investigation.
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Affiliation(s)
- Lia J Zallar
- Section on Clinical Psychoneuroendocrinology and Neuropsychopharmacology, National Institute on Alcohol Abuse and Alcoholism Division of Intramural Clinical and Biological Research, and National Institute on Drug Abuse Intramural Research Program, National Institutes of Health, Bethesda, Maryland
- Neurobiology of Addiction Section, National Institute on Drug Abuse Intramural Research Program, National Institutes of Health, Baltimore, Maryland
| | - Silvia Beurmann
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, Maryland
| | - Brendan J Tunstall
- Neurobiology of Addiction Section, National Institute on Drug Abuse Intramural Research Program, National Institutes of Health, Baltimore, Maryland
| | - Claire M Fraser
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, Maryland
- Department of Medicine, University of Maryland School of Medicine, Baltimore, Maryland
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland
| | - George F Koob
- Neurobiology of Addiction Section, National Institute on Drug Abuse Intramural Research Program, National Institutes of Health, Baltimore, Maryland
| | - Leandro F Vendruscolo
- Neurobiology of Addiction Section, National Institute on Drug Abuse Intramural Research Program, National Institutes of Health, Baltimore, Maryland
| | - Lorenzo Leggio
- Section on Clinical Psychoneuroendocrinology and Neuropsychopharmacology, National Institute on Alcohol Abuse and Alcoholism Division of Intramural Clinical and Biological Research, and National Institute on Drug Abuse Intramural Research Program, National Institutes of Health, Bethesda, Maryland
- Department of Behavioral and Social Sciences, Center for Alcohol and Addiction Studies, Brown University, Providence, Rhode Island
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Ratcliff M, Rees D, McGrady S, Buntwal L, Hornsby AKE, Bayliss J, Kent BA, Bussey T, Saksida L, Beynon AL, Howell OW, Morgan AH, Sun Y, Andrews ZB, Wells T, Davies JS. Calorie restriction activates new adult born olfactory-bulb neurones in a ghrelin-dependent manner but acyl-ghrelin does not enhance subventricular zone neurogenesis. J Neuroendocrinol 2019; 31:e12755. [PMID: 31179562 DOI: 10.1111/jne.12755] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Revised: 06/06/2019] [Accepted: 06/06/2019] [Indexed: 12/25/2022]
Abstract
The ageing and degenerating brain show deficits in neural stem/progenitor cell (NSPC) plasticity that are accompanied by impairments in olfactory discrimination. Emerging evidence suggests that the gut hormone ghrelin plays an important role in protecting neurones, promoting synaptic plasticity and increasing hippocampal neurogenesis in the adult brain. In the present study, we investigated the role of ghrelin with respect to modulating adult subventricular zone (SVZ) NSPCs that give rise to new olfactory bulb (OB) neurones. We characterised the expression of the ghrelin receptor, growth hormone secretagogue receptor (GHSR), using an immunohistochemical approach in GHSR-eGFP reporter mice to show that GHSR is expressed in several regions, including the OB but not in the SVZ of the lateral ventricle. These data suggest that acyl-ghrelin does not mediate a direct effect on NSPC in the SVZ. Consistent with these findings, treatment with acyl-ghrelin or genetic silencing of GHSR did not alter NSPC proliferation within the SVZ. Similarly, using a bromodeoxyuridine pulse-chase approach, we show that peripheral treatment of adult rats with acyl-ghrelin did not increase the number of new adult-born neurones in the granule cell layer of the OB. These data demonstrate that acyl-ghrelin does not increase adult OB neurogenesis. Finally, we investigated whether elevating ghrelin indirectly, via calorie restriction (CR), regulated the activity of new adult-born cells in the OB. Overnight CR induced c-Fos expression in new adult-born OB cells but not in developmentally born cells, whereas neuronal activity was absent following re-feeding. These effects were not present in ghrelin-/- mice, suggesting that adult-born cells are uniquely sensitive to changes in ghrelin mediated by fasting and re-feeding. In summary, ghrelin does not promote neurogenesis in the SVZ and OB; however, new adult-born OB cells are activated by CR in a ghrelin-dependent manner.
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Affiliation(s)
- Michael Ratcliff
- Molecular Neurobiology, Institute of Life Sciences, School of Medicine, Swansea University, Swansea, UK
| | - Daniel Rees
- Molecular Neurobiology, Institute of Life Sciences, School of Medicine, Swansea University, Swansea, UK
| | - Scott McGrady
- Molecular Neurobiology, Institute of Life Sciences, School of Medicine, Swansea University, Swansea, UK
| | - Luke Buntwal
- Molecular Neurobiology, Institute of Life Sciences, School of Medicine, Swansea University, Swansea, UK
| | - Amanda K E Hornsby
- Molecular Neurobiology, Institute of Life Sciences, School of Medicine, Swansea University, Swansea, UK
| | - Jaqueline Bayliss
- Biomedical Discovery Unit, Department of Physiology, Monash University, Melbourne, Victoria, Australia
| | - Brianne A Kent
- Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | | | | | - Amy L Beynon
- Molecular Neurobiology, Institute of Life Sciences, School of Medicine, Swansea University, Swansea, UK
| | - Owain W Howell
- Molecular Neurobiology, Institute of Life Sciences, School of Medicine, Swansea University, Swansea, UK
| | - Alwena H Morgan
- Molecular Neurobiology, Institute of Life Sciences, School of Medicine, Swansea University, Swansea, UK
| | - Yuxiang Sun
- Department of Nutrition and Food Science, Texas A&M University, College Station, Texas, USA
| | - Zane B Andrews
- Biomedical Discovery Unit, Department of Physiology, Monash University, Melbourne, Victoria, Australia
| | - Timothy Wells
- School of Biosciences, Cardiff University, Cardiff, UK
| | - Jeffrey S Davies
- Molecular Neurobiology, Institute of Life Sciences, School of Medicine, Swansea University, Swansea, UK
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Napolitano T, Silvano S, Vieira A, Balaji S, Garrido-Utrilla A, Friano ME, Atlija J, Collombat P. Role of ghrelin in pancreatic development and function. Diabetes Obes Metab 2018; 20 Suppl 2:3-10. [PMID: 30230184 DOI: 10.1111/dom.13385] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Revised: 05/23/2018] [Accepted: 05/25/2018] [Indexed: 11/28/2022]
Abstract
Ghrelin is a gastric peptide with anabolic functions. It acutely stimulates growth hormone (GH) secretion from the anterior pituitary glands and modulates hypothalamic circuits that control food intake and energy expenditure. Besides its central activity, ghrelin is also involved in the regulation of pancreatic development and physiology. Particularly, several studies highlighted the ability of ghrelin to sustain β-cell viability and proliferation. Furthermore, ghrelin seems to exert inhibitory effects on pancreatic acinar and endocrine secretory functions. Due to its pleiotropic activity on energy metabolism, ghrelin has become a topic of great interest for experimental research focused on type II diabetes and obesity. The aim of this review is to illustrate the complex and not fully understood interplay between ghrelin, pancreas and glucose homeostasis.
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Affiliation(s)
- Tiziana Napolitano
- Inserm, CNRS, iBV, University of Nice Sophia Antipolis, Nice, France
- iBV, Institut de Biologie Valrose, Centre de Biochimie, University of Nice Sophia Antipolis, Nice Cedex 2, France
| | - Serena Silvano
- Inserm, CNRS, iBV, University of Nice Sophia Antipolis, Nice, France
- iBV, Institut de Biologie Valrose, Centre de Biochimie, University of Nice Sophia Antipolis, Nice Cedex 2, France
| | - Andhira Vieira
- Inserm, CNRS, iBV, University of Nice Sophia Antipolis, Nice, France
- iBV, Institut de Biologie Valrose, Centre de Biochimie, University of Nice Sophia Antipolis, Nice Cedex 2, France
| | - Shruti Balaji
- Inserm, CNRS, iBV, University of Nice Sophia Antipolis, Nice, France
- iBV, Institut de Biologie Valrose, Centre de Biochimie, University of Nice Sophia Antipolis, Nice Cedex 2, France
| | - Anna Garrido-Utrilla
- Inserm, CNRS, iBV, University of Nice Sophia Antipolis, Nice, France
- iBV, Institut de Biologie Valrose, Centre de Biochimie, University of Nice Sophia Antipolis, Nice Cedex 2, France
| | - Marika E Friano
- Inserm, CNRS, iBV, University of Nice Sophia Antipolis, Nice, France
- iBV, Institut de Biologie Valrose, Centre de Biochimie, University of Nice Sophia Antipolis, Nice Cedex 2, France
| | - Josipa Atlija
- Inserm, CNRS, iBV, University of Nice Sophia Antipolis, Nice, France
- iBV, Institut de Biologie Valrose, Centre de Biochimie, University of Nice Sophia Antipolis, Nice Cedex 2, France
| | - Patrick Collombat
- Inserm, CNRS, iBV, University of Nice Sophia Antipolis, Nice, France
- iBV, Institut de Biologie Valrose, Centre de Biochimie, University of Nice Sophia Antipolis, Nice Cedex 2, France
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Li N, Song G, Wang Y, Zhu Q, Han F, Zhang C, Zhou Y. Blocking constitutive activity of GHSR1a in the lateral amygdala facilitates acquisition of conditioned taste aversion. Neuropeptides 2018; 68:22-27. [PMID: 29254662 DOI: 10.1016/j.npep.2017.12.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/29/2017] [Revised: 11/05/2017] [Accepted: 12/05/2017] [Indexed: 11/28/2022]
Abstract
Ghrelin is a circulating peptide hormone promoting feeding and regulating energy metabolism in human and rodents. Ghrelin functions by binding to its receptor, the growth hormone secretagogue receptor 1a (GHSR1a), which are widely distributed throughout the brain including the amygdala, a brain region important for regulating valenced behavior, such as aversion. Interestingly, GHSR1a was once characterized by highly constitutive, ligand-independent activity. However, the physiological importance of such ligand-independent signaling on aversive memory processing has not been tested yet. Here, we applied [D-Arg1, D-Phe5, D-Trp7,9, Leu11]-Substance P (D-SP), a full inverse agonist for GHSR1a, into the lateral amygdala (LA) and investigated the effect of blocking GHSR1a constitutive activity on conditioned taste aversion (CTA) in rats. We found that intra-LA infusion of a single low dose of D-SP (8ng/0.5μl/side) facilitates CTA acquisition. Moreover, pre-administration of a high dose of D-SP into the LA abolishes the suppressive effect of exogenous ghrelin on CTA acquisition. In contrast, pre-administration of the same dose of D-SP does not affect the suppression of substance P, a potent neurokinin-1 (NK1) receptor ligand, on CTA. Therefore, our data indicated that the spontaneous or basal activity of GHSR1a signaling in the LA might interfere with CTA memory formation. D-SP decreases the constitutive activity of GHSR1a and thus facilitates CTA. Altogether, our present findings along with previous results support the idea that ghrelin/GHSR1a signaling in the LA circuit blocks conditioned taste aversion.
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Affiliation(s)
- Nan Li
- Department of Physiology, Medical College of Qingdao University, Qingdao 266071, Shandong, China
| | - Ge Song
- Department of Physiology, Medical College of Qingdao University, Qingdao 266071, Shandong, China
| | - Yaohui Wang
- Department of Physiology, Medical College of Qingdao University, Qingdao 266071, Shandong, China
| | - Qianqian Zhu
- Department of Physiology, Medical College of Qingdao University, Qingdao 266071, Shandong, China
| | - Fubing Han
- Department of Physiology, Medical College of Qingdao University, Qingdao 266071, Shandong, China
| | - Chonghui Zhang
- Department of Physiology, Medical College of Qingdao University, Qingdao 266071, Shandong, China
| | - Yu Zhou
- Department of Physiology, Medical College of Qingdao University, Qingdao 266071, Shandong, China.
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Fernandez G, Cabral A, Andreoli MF, Labarthe A, M'Kadmi C, Ramos JG, Marie J, Fehrentz JA, Epelbaum J, Tolle V, Perello M. Evidence Supporting a Role for Constitutive Ghrelin Receptor Signaling in Fasting-Induced Hyperphagia in Male Mice. Endocrinology 2018; 159:1021-1034. [PMID: 29300858 DOI: 10.1210/en.2017-03101] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Accepted: 12/21/2017] [Indexed: 01/22/2023]
Abstract
Ghrelin is a potent orexigenic peptide hormone that acts through the growth hormone secretagogue receptor (GHSR), a G protein-coupled receptor highly expressed in the hypothalamus. In vitro studies have shown that GHSR displays a high constitutive activity, whose physiological relevance is uncertain. As GHSR gene expression in the hypothalamus is known to increase in fasting conditions, we tested the hypothesis that constitutive GHSR activity at the hypothalamic level drives the fasting-induced hyperphagia. We found that refed wild-type (WT) mice displayed a robust hyperphagia that continued for 5 days after refeeding and changed their food intake daily pattern. Fasted WT mice showed an increase in plasma ghrelin levels, as well as in GHSR expression levels and ghrelin binding sites in the hypothalamic arcuate nucleus. When fasting-refeeding responses were evaluated in ghrelin- or GHSR-deficient mice, only the latter displayed an ∼15% smaller hyperphagia, compared with WT mice. Finally, fasting-induced hyperphagia of WT mice was significantly smaller in mice centrally treated with the GHSR inverse agonist K-(D-1-Nal)-FwLL-NH2, compared with mice treated with vehicle, whereas it was unaffected in mice centrally treated with the GHSR antagonists D-Lys3-growth hormone-releasing peptide 6 or JMV2959. Taken together, genetic models and pharmacological results support the notion that constitutive GHSR activity modulates the magnitude of the compensatory hyperphagia triggered by fasting. Thus, the hypothalamic GHSR signaling system could affect the set point of daily food intake, independently of plasma ghrelin levels, in situations of negative energy balance.
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Affiliation(s)
- Gimena Fernandez
- Laboratory of Neurophysiology of the Multidisciplinary Institute of Cell Biology (Argentine Research Council, Scientific Research Commission of the Province of Buenos Aires and National University of La Plata), La Plata, Buenos Aires, Argentina
| | - Agustina Cabral
- Laboratory of Neurophysiology of the Multidisciplinary Institute of Cell Biology (Argentine Research Council, Scientific Research Commission of the Province of Buenos Aires and National University of La Plata), La Plata, Buenos Aires, Argentina
| | - María F Andreoli
- School of Biochemistry and Biological Sciences, National University of Litoral and Institute of Environmental Health, Santa Fe, Argentina
| | - Alexandra Labarthe
- Centre de Psychiatrie et Neurosciences Unité Mixte de Recherche Scientifique_S894 INSERM Université Paris Descartes, Sorbonne Paris-Cité, Paris, France
| | - Céline M'Kadmi
- Institut des Biomolécules Max Mousseron, Unité Mixte de Recherche Scientifique 5247 Centre National de la Recherche Scientifique-Université Montpellier-École Nationale Supérieure de Chimie de Montpellier, Faculté de Pharmacie, Montpellier, France
| | - Jorge G Ramos
- School of Biochemistry and Biological Sciences, National University of Litoral and Institute of Environmental Health, Santa Fe, Argentina
| | - Jacky Marie
- Institut des Biomolécules Max Mousseron, Unité Mixte de Recherche Scientifique 5247 Centre National de la Recherche Scientifique-Université Montpellier-École Nationale Supérieure de Chimie de Montpellier, Faculté de Pharmacie, Montpellier, France
| | - Jean-Alain Fehrentz
- Institut des Biomolécules Max Mousseron, Unité Mixte de Recherche Scientifique 5247 Centre National de la Recherche Scientifique-Université Montpellier-École Nationale Supérieure de Chimie de Montpellier, Faculté de Pharmacie, Montpellier, France
| | - Jacques Epelbaum
- Centre de Psychiatrie et Neurosciences Unité Mixte de Recherche Scientifique_S894 INSERM Université Paris Descartes, Sorbonne Paris-Cité, Paris, France
- Mécanismes Adaptatifs et Evolution, Unité Mixte de Recherche Scientifique 7179 Centre National de la Recherche Scientifique, Muséum National d'Histoire Naturelle France, Brunoy, France
| | - Virginie Tolle
- Centre de Psychiatrie et Neurosciences Unité Mixte de Recherche Scientifique_S894 INSERM Université Paris Descartes, Sorbonne Paris-Cité, Paris, France
| | - Mario Perello
- Laboratory of Neurophysiology of the Multidisciplinary Institute of Cell Biology (Argentine Research Council, Scientific Research Commission of the Province of Buenos Aires and National University of La Plata), La Plata, Buenos Aires, Argentina
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11
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Abstract
Obesity, a major risk factor for the development of diabetes mellitus, cardiovascular diseases and certain types of cancer, arises from a chronic positive energy balance that is often due to unlimited access to food and an increasingly sedentary lifestyle on the background of a genetic and epigenetic vulnerability. Our understanding of the humoral and neuronal systems that mediate the control of energy homeostasis has improved dramatically in the past few decades. However, our ability to develop effective strategies to slow the current epidemic of obesity has been hampered, largely owing to the limited knowledge of the mechanisms underlying resistance to the action of metabolic hormones such as leptin and ghrelin. The development of resistance to leptin and ghrelin, hormones that are crucial for the neuroendocrine control of energy homeostasis, is a hallmark of obesity. Intensive research over the past several years has yielded tremendous progress in our understanding of the cellular pathways that disrupt the action of leptin and ghrelin. In this Review, we discuss the molecular mechanisms underpinning resistance to leptin and ghrelin and how they can be exploited as targets for pharmacological management of obesity.
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Affiliation(s)
- Huxing Cui
- Department of Pharmacology, University of Iowa, Iowa City, Iowa 52246, USA
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa 52242, USA
| | - Miguel López
- Department of Physiology, Center for Research in Molecular Medicine and Chronic Diseases (CiMUS), University of Santiago de Compostela-Instituto de Investigación Sanitaria, Santiago de Compostela 15782, Spain
- Centro de Investigación Biomédica en Red-Fisiopatología de la Obesidad y Nutrición (CIBERobn), Santiago de Compostela 15706, Spain
| | - Kamal Rahmouni
- Department of Pharmacology, University of Iowa, Iowa City, Iowa 52246, USA
- Fraternal Order of Eagles Diabetes Research Center, University of Iowa, Iowa City, Iowa 52242, USA
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12
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Bake T, Hellgren KT, Dickson SL. Acute ghrelin changes food preference from a high-fat diet to chow during binge-like eating in rodents. J Neuroendocrinol 2017; 29:10.1111/jne.12463. [PMID: 28219000 PMCID: PMC5434925 DOI: 10.1111/jne.12463] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2016] [Revised: 01/25/2017] [Accepted: 02/16/2017] [Indexed: 01/20/2023]
Abstract
Ghrelin, an orexigenic hormone released from the empty stomach, provides a gut-brain signal that promotes many appetitive behaviours, including anticipatory and goal-directed behaviours for palatable treats high in sugar and/or fat. In the present study, we aimed to determine whether ghrelin is able to influence and/or may even have a role in binge-like eating behaviour in rodents. Accordingly, we used a palatable scheduled feeding (PSF) paradigm in which ad lib. chow-fed rodents are trained to 'binge' on a high-fat diet (HFD) offered each day for a limited period of 2 hours. After 2 weeks of habituation to this paradigm, on the test day and immediately prior to the 2-hour PSF, rats were administered ghrelin or vehicle solution by the i.c.v. route. Remarkably and unexpectedly, during the palatable scheduled feed, when rats normally only binge on the HFD, those injected with i.c.v. ghrelin started to eat more chow and chow intake remained above baseline for the rest of the 24-hour day. We identify the ventral tegmental area (VTA) (a key brain area involved in food reward) as a substrate involved because these effects could be reproduced, in part, by intra-VTA delivery of ghrelin. Fasting, which increases endogenous ghrelin, immediately prior to a palatable schedule feed also increased chow intake during/after the schedule feed but, in contrast to ghrelin injection, did not reduce HFD intake. Chronic continuous central ghrelin infusion over several weeks enhanced binge-like behaviour in palatable schedule fed rats. Over a 4-week period, GHS-R1A-KO mice were able to adapt and maintain large meals of HFD in a manner similar to wild-type mice, suggesting that ghrelin signalling may not have a critical role in the acquisition or maintenance in this kind of feeding behaviour. In conclusion, ghrelin appears to act as a modulating factor for binge-like eating behaviour by shifting food preference towards a more nutritious choice (from HFD to chow), with these effects being somewhat divergent from fasting.
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Affiliation(s)
- T. Bake
- Department of Physiology/EndocrineInstitute of Neuroscience and PhysiologyThe Sahlgrenska Academy at the University of GothenburgGothenburgSweden
| | - K. T. Hellgren
- Department of Physiology/EndocrineInstitute of Neuroscience and PhysiologyThe Sahlgrenska Academy at the University of GothenburgGothenburgSweden
| | - S. L. Dickson
- Department of Physiology/EndocrineInstitute of Neuroscience and PhysiologyThe Sahlgrenska Academy at the University of GothenburgGothenburgSweden
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13
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Abstract
Ghrelin is a pleiotropic hormone, whose effect on growth hormone secretion, through the growth hormone secretagogue (GHS) receptor, is one of its many actions. Relationships between GHS receptor gene variants and human height, both in healthy individuals and in patients with growth disorders have been identified. These include constitutional delay in growth and puberty, idiopathic short stature, and isolated growth hormone deficiency. In this review, we provide an overview of the role of ghrelin in growth.
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14
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Fernandez G, Cabral A, Cornejo MP, De Francesco PN, Garcia-Romero G, Reynaldo M, Perello M. Des-Acyl Ghrelin Directly Targets the Arcuate Nucleus in a Ghrelin-Receptor Independent Manner and Impairs the Orexigenic Effect of Ghrelin. J Neuroendocrinol 2016; 28:12349. [PMID: 26661382 DOI: 10.1111/jne.12349] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Revised: 11/12/2015] [Accepted: 12/06/2015] [Indexed: 12/16/2022]
Abstract
Ghrelin is a stomach-derived octanoylated peptide hormone that plays a variety of well-established biological roles acting via its specific receptor known as growth hormone secretagogue receptor (GHSR). In plasma, a des-octanoylated form of ghrelin, named des-acyl ghrelin (DAG), also exists. DAG is suggested to be a signalling molecule that has specific targets, including the brain, and regulates some physiological functions. However, no specific receptor for DAG has been reported until now, and, consequently, the potential role of DAG as a hormone has remained a matter of debate. In the present study, we show that DAG specifically binds to and acts on a subset of arcuate nucleus (ARC) cells in a GHSR-independent manner. ARC cells labelled by a DAG fluorescent tracer include the neuropeptide Y (NPY) and non-NPY neurones. Given the well-established role of the ARC in appetite regulation, we tested the effect of centrally administered DAG on food intake. We found that DAG failed to affect dark phase feeding, as well as food intake, after a starvation period; however, it impaired the orexigenic actions of peripherally administered ghrelin. Thus, we conclude that DAG directly targets ARC neurones and antagonises the orexigenic effects of peripherally administered ghrelin.
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Affiliation(s)
- G Fernandez
- Laboratory of Neurophysiology of the Multidisciplinary Institute of Cell Biology, [IMBICE dependent on the Argentine Research Council (CONICET) and Scientific Research Commission, Province of Buenos Aires (CIC-PBA)], La Plata, Buenos Aires, Argentina
| | - A Cabral
- Laboratory of Neurophysiology of the Multidisciplinary Institute of Cell Biology, [IMBICE dependent on the Argentine Research Council (CONICET) and Scientific Research Commission, Province of Buenos Aires (CIC-PBA)], La Plata, Buenos Aires, Argentina
| | - M P Cornejo
- Laboratory of Neurophysiology of the Multidisciplinary Institute of Cell Biology, [IMBICE dependent on the Argentine Research Council (CONICET) and Scientific Research Commission, Province of Buenos Aires (CIC-PBA)], La Plata, Buenos Aires, Argentina
| | - P N De Francesco
- Laboratory of Neurophysiology of the Multidisciplinary Institute of Cell Biology, [IMBICE dependent on the Argentine Research Council (CONICET) and Scientific Research Commission, Province of Buenos Aires (CIC-PBA)], La Plata, Buenos Aires, Argentina
| | - G Garcia-Romero
- Laboratory of Neurophysiology of the Multidisciplinary Institute of Cell Biology, [IMBICE dependent on the Argentine Research Council (CONICET) and Scientific Research Commission, Province of Buenos Aires (CIC-PBA)], La Plata, Buenos Aires, Argentina
| | - M Reynaldo
- Laboratory of Neurophysiology of the Multidisciplinary Institute of Cell Biology, [IMBICE dependent on the Argentine Research Council (CONICET) and Scientific Research Commission, Province of Buenos Aires (CIC-PBA)], La Plata, Buenos Aires, Argentina
| | - M Perello
- Laboratory of Neurophysiology of the Multidisciplinary Institute of Cell Biology, [IMBICE dependent on the Argentine Research Council (CONICET) and Scientific Research Commission, Province of Buenos Aires (CIC-PBA)], La Plata, Buenos Aires, Argentina
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15
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Beheshti S, Shahrokhi S. Blocking the ghrelin receptor type 1a in the rat brain impairs memory encoding. Neuropeptides 2015; 52:97-102. [PMID: 26072187 DOI: 10.1016/j.npep.2015.05.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Revised: 05/18/2015] [Accepted: 05/21/2015] [Indexed: 12/17/2022]
Abstract
Studies have shown that intracerebral administration of ghrelin hormone affects learning and memory in different experimental models of learning. However, the effect of antagonism of ghrelin receptor type 1a (GHS-R1a) on different stages of learning has not been investigated. In this study the effect of intracerebroventricular (i.c.v) injection of a GHS-R1a selective antagonist (d-Lys-3-GHRP-6) was examined on acquisition and consolidation of learning in the passive avoidance task. In total, 72 male Wistar rats weighing 230-280g were randomly distributed into 9 groups of 8 each. Animals underwent stereotaxic surgery and cannulated in their right ventricle. One week after surgery, the rats received different doses of d-Lys-3-GHRP-6 (0.2, 2, 20 and 80nM/5μl; i.c.v) 10min before, or (2, 20 and 80nM/5μl; i.c.v) immediately after training. The control groups received solvent of the drug. Twenty four hours later in the test day, memory retrieval was assessed. Pre-training injection of d-Lys-3-GHRP-6 decreased step-through latency (STL) and increased number of step-throughs into the dark compartment (NST) in a dose-dependent manner, but failed to be statistically significant. It also increased time spent in the dark compartment (TDC), significantly and in a dose-dependent manner. Post-training injection of d-Lys-3-GHRP-6 decreased step-through latency and increased time spent in the dark compartment and number of step-throughs into the dark compartment, significantly and in a dose-dependent manner. The results indicate that antagonism of the GHS-R1a in the rat brain impairs memory encoding on both acquisition and consolidation stages. Further studies are required to elucidate the main brain regions affected by the antagonist.
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Affiliation(s)
- Siamak Beheshti
- Division of Animal Sciences, Department of Biology, Faculty of Sciences, University of Isfahan, Isfahan, Iran.
| | - Shahrzad Shahrokhi
- Division of Animal Sciences, Department of Biology, Faculty of Sciences, University of Isfahan, Isfahan, Iran
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16
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Hirayama H, Mominoki K, Shiina T, Shimizu Y. [Effect of ghrelin on colonic motility]. Nihon Yakurigaku Zasshi 2014; 143:270-274. [PMID: 24919551 DOI: 10.1254/fpj.143.270] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
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Abstract
PURPOSE OF REVIEW Muscle wasting is a comorbidity often associated with a wide range of disorders that severely affects patient prognosis and quality of life. Ghrelin, through its receptor GHSR-1a, stimulates appetite and growth hormone (GH) release. Several studies indicate that ghrelin administration is a valid treatment for cachexia because it improves muscle mass and function, likely by restoring a positive energy balance. RECENT FINDINGS In addition to its GHSR-1a-mediated effects on muscle mass, ghrelin acts directly on skeletal muscle, wherein it exerts a protective activity against muscle wasting. This direct activity is independent of GHSR-1a and is shared by the unacylated form of ghrelin, which does not bind GHSR-1a and is devoid of the effects on appetite and GH release. SUMMARY Both the acylated and unacylated forms of ghrelin might have therapeutic potential for the treatment of skeletal muscle wasting.
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Affiliation(s)
- Simone Reano
- Department of Translational Medicine, Università del Piemonte Orientale 'A. Avogadro', Novara, Italy
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18
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Pei XM, Yung BY, Yip SP, Ying M, Benzie IF, Siu PM. Desacyl ghrelin prevents doxorubicin-induced myocardial fibrosis and apoptosis via the GHSR-independent pathway. Am J Physiol Endocrinol Metab 2014; 306:E311-23. [PMID: 24326424 DOI: 10.1152/ajpendo.00123.2013] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Doxorubicin is an effective chemotherapeutic agent used to treat malignancies, but it causes cardiomyopathy. Preliminary evidence suggests that desacyl ghrelin might have protective effects on doxorubicin cardiotoxicity. This study examined the cellular effects of desacyl ghrelin on myocardial fibrosis and apoptosis in a doxorubicin cardiomyopathy experimental model. Adult C57BL/6 mice received an intraperitoneal injection of doxorubicin to induce cardiomyopathy, followed by 4-day treatment of saline (control) or desacyl ghrelin with or without [d-Lys3]-GHRP-6 (a growth hormone secretagogue receptor or GHSR1a antagonist). Ventricular structural and functional parameters were evaluated by transthoracic echocardiography. Molecular and cellular measurements were performed in ventricular muscle to examine myocardial fibrosis and apoptosis. Cardiac dysfunction was induced by doxorubicin, as indicated by significant decreases in ventricular fractional shortening and ejection fraction. This doxorubicin-induced cardiac dysfunction was prevented by the treatment of desacyl ghrelin no matter with or without the presence of [d-Lys3]-GHRP-6. Doxorubicin induced fibrosis (accumulated collagen deposition and increased CTGF), activated apoptosis (increased TUNEL index, apoptotic DNA fragmentation, and caspase-3 activity and decreased Bcl-2/Bax ratio), and suppressed phosphorylation status of prosurvival signals (ERK1/2 and Akt) in ventricular muscles. All these molecular and cellular alterations induced by doxorubicin were not found in the animals treated with desacyl ghrelin. Notably, the changes in the major markers of apoptosis, fibrosis, and Akt phosphorylation were found to be similar in the animals following the treatment of desacyl ghrelin with and without GHSR antagonist [d-Lys3]-GHRP-6. These findings demonstrate clearly that desacyl ghrelin protects the cardiomyocytes against the doxorubicin-induced cardiomyopathy by preventing the activation of cardiac fibrosis and apoptosis, and the effects are probably mediated through GHSR-independent mechanism.
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Affiliation(s)
- Xiao M Pei
- Department of Health Technology and Informatics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China
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19
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Chen X, Chen Q, Wang L, Li G. Ghrelin induces cell migration through GHSR1a-mediated PI3K/Akt/eNOS/NO signaling pathway in endothelial progenitor cells. Metabolism 2013; 62:743-52. [PMID: 23218924 DOI: 10.1016/j.metabol.2012.09.014] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Revised: 09/16/2012] [Accepted: 09/24/2012] [Indexed: 01/18/2023]
Abstract
OBJECTIVE The purpose of this research was to investigate the effects of ghrelin on circulating endothelial progenitor cells (EPC) directional migration and its underlying molecular mechanisms involved in this process. MATERIALS/METHODS EPC were isolated from bone marrow of SD rats by using Percoll density gradient centrifugation, and characterized by double positive for acLDL-Dil uptake and FITC-UEA-1 binding and immunocytochemistry for CD34, CD133, vWF and Flk-1. EPC were treated with different concentrations of ghrelin (10(-9)~10(-6)M) with or without GHSR1a inhibitor [D-Lys3]-GHRP-6, PI3K inhibitor LY294002 and endothelial nitric oxide synthase (eNOS) inhibitor L-NAME, migration of EPC was detected by transwell assay, levels of phosphorylated and total Akt and eNOS were determined by Western-blot analysis and Nitric Oxide (NO) production was measured by Griess assay, respectively. RESULTS EPC were successfully obtained by Percoll density gradient centrifugation and ghrelin at 10(-8)M~10(-7)M promoted EPC migration. Ghrelin-induced EPC migration was accompanied by phosphorylation of Akt and eNOS, as well as an increase in NO production. These biochemical events and EPC directional migration induced by ghrelin were completely inhibited by GHSR-1a blocker [D-Lys3]-GHRP-6. PI3K inhibitor LY294002 attenuated ghrelin-induced EPC migration, phosphorylation of Akt and eNOS, and NO production. eNOS inhibitor L-NAME blocked ghrelin-induced EPC migration, phosphorylation of eNOS, and NO production, but had no effect on Akt phosphorylation. CONCLUSIONS These findings suggest that ghrelin stimulates EPC directional migration via GHSR1a-mediated PI3K/Akt/eNOS/NO signal pathway. It indicates that ghrelin may be used as a therapeutic strategy to treat ischemic diseases by promoting EPC directional migration.
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Affiliation(s)
- Xiaodong Chen
- Department of Geriatrics, the Second Affiliated Hospital of Chongqing Medical University, Chongqing 400010, China
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20
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Patterson ZR, Khazall R, Mackay H, Anisman H, Abizaid A. Central ghrelin signaling mediates the metabolic response of C57BL/6 male mice to chronic social defeat stress. Endocrinology 2013; 154:1080-91. [PMID: 23341196 DOI: 10.1210/en.2012-1834] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Chronic stressors promote metabolic disturbances, including obesity and metabolic syndrome. Ghrelin, a peptide that promotes appetite and the accumulation of adipose tissue, is also secreted in response to stressors to protect the brain and peripheral tissues from the effects of these stressors. Here we demonstrate that elevated ghrelin levels produced by chronic exposure to social stress are associated with increased caloric intake and body weight gain in male C57BL mice. In contrast, stressed mice lacking ghrelin receptors (GHSR KO mice) or C57BL mice receiving chronic intracerebroventricular delivery of the ghrelin receptor antagonist [d-Lys(3)]-GHRP-6 show attenuated weight gain and feeding responses under the same social stress paradigm. Interestingly, stressed GHSR KO mice showed depleted sc and intrascapular brown fat depots, whereas stressed young wild-type mice did not. In old wild-type mice, chronic social defeat increased visceral and intrascapular brown fat depots in association with increases in obesity markers like hyperleptinemia and hyperinsulinemia along with increased hypothalamic expression of neuropeptide Y and Agouti related peptide. Importantly, the elevated expression of these peptides persisted least for 2 weeks after cessation of the stressor regimen. In contrast, old GHSR KO mice did not show these alterations after chronic social defeat. These results suggest that ghrelin plays an important role in the metabolic adaptations necessary to meet the energetic demands posed by stressors, but chronic exposure to stress-induced ghrelin elevations ultimately could lead to long lasting metabolic dysfunctions.
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MESH Headings
- Adipose Tissue, Brown/pathology
- Aging/pathology
- Aging/physiology
- Aging/psychology
- Animals
- Behavior, Animal/physiology
- Energy Intake/physiology
- Ghrelin/antagonists & inhibitors
- Ghrelin/blood
- Ghrelin/physiology
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Models, Biological
- Obesity/pathology
- Obesity/physiopathology
- Obesity/psychology
- Receptors, Ghrelin/deficiency
- Receptors, Ghrelin/genetics
- Receptors, Ghrelin/physiology
- Signal Transduction/physiology
- Social Behavior
- Stress, Physiological
- Stress, Psychological
- Weight Gain/physiology
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Affiliation(s)
- Z R Patterson
- Department of Neuroscience, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario, K1S 5B6, Canada
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21
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Abstract
The growth hormone (GH) secretagogue receptor (GHS-R1a) is a G protein-coupled receptor (GPCR) expressed in the brain as well as other areas of the body. In the early 1990s, this receptor was expression cloned in MERCK laboratories by using a group of synthesized small molecules known to increase GH release in humans and other animals. Since its discovery, hundreds of studies have shown the importance of this receptor and its endogenous ligand, ghrelin, in metabolism, neurotransmission, and behavior. Even more relevant are the prospective benefits that will result from pharmacologic manipulation of GHS-R1a. Multiple GHS-R1a agonists and antagonists are available for experimentation, and some have been used in patients with promising results. Studies in rodents have revealed intriguing potential roles for GHS-R1a modulation. Our goal in this chapter is to connect these studies with the inherent advantages of targeting this receptor pharmacologically.
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Affiliation(s)
- Rosie G Albarrán-Zeckler
- Smith Laboratory, Department of Metabolism and Aging, The Scripps Research Institute, Scripps Florida, Jupiter, Fla. 33458, USA
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22
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Title page / table of contents / preface. Endocr Dev 2013; 25:I-VIII. [PMID: 23652404 DOI: 10.1159/000350166] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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23
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Abstract
Ghrelin was originally identified as a growth hormone secretagogue, but later studies suggested that it plays an important role in the regulation of appetite and body weight. The implication of genetic variants of the ghrelin-ghrelin receptor axis in the determination of stature, appetite, body weight, glucose metabolism and eating disorders has been the focus of numerous small and larger studies. More recently, several studies have shown some involvement of ghrelin and growth hormone secretagogue receptor (GHSR) genetic variants in some cancers, or their role in the genetics of immune diseases or addictive behaviour. The overall results suggest that the effects of common genetic variants are lacking or modest, while rare sequence alteration may lead to disease status in individual patients. In this review we summarize the available data on the genetics of ghrelin axis in humans.
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Affiliation(s)
- Maria Gueorguiev
- Centre for Endocrinology, William Harvey Research Institute, Barts and the London School of Medicine, Queen Mary University of London, London EC1M 6BQ, UK
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24
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Abstract
Since the original discovery of ghrelin and, subsequently, obestatin (the alternative product of the ghrelin gene), a major interest has been devoted to the investigation of their central and peripheral activities in physiological conditions as well as on their role in metabolic diseases. However, several studies with different methodological approaches variably identified ghrelin and obestatin synthesis and secretion in several neoplastic conditions, including neuroendocrine and non-neuroendocrine cancers of various sites. Moreover, in vitro studies showed the capability of ghrelin to modulate tumor cell functions such as cell proliferation, apoptosis and invasiveness, although with variable and even paradoxical effects in different cell models. Interestingly, in most studies, it was demonstrated that ghrelin exerts its pro- or antineoplastic properties by means of receptors other than GHSR1a, that still need to be identified. However, the possible usefulness of the modulation of the ghrelin/obestatin axis in neoplastic conditions using either synthetic agonists or antagonists, though interesting in perspective, is still far from clinical applicability, and probably more related to the regulation of specific metabolic pathways in tumor cells, including lipid and carbohydrate use, than to the specific modulation of cell proliferation.
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Affiliation(s)
- Mauro Papotti
- Department of Clinical and Biological Sciences, University of Turin at San Luigi Hospital, IT-10043 Orbassano, Turin, Italy.
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Hansson C, Shirazi RH, Näslund J, Vogel H, Neuber C, Holm G, Anckarsäter H, Dickson SL, Eriksson E, Skibicka KP. Ghrelin influences novelty seeking behavior in rodents and men. PLoS One 2012; 7:e50409. [PMID: 23227170 PMCID: PMC3515575 DOI: 10.1371/journal.pone.0050409] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2012] [Accepted: 10/19/2012] [Indexed: 12/13/2022] Open
Abstract
Recent discoveries indicate an important role for ghrelin in drug and alcohol reward and an ability of ghrelin to regulate mesolimbic dopamine activity. The role of dopamine in novelty seeking, and the association between this trait and drug and alcohol abuse, led us to hypothesize that ghrelin may influence novelty seeking behavior. To test this possibility we applied several complementary rodent models of novelty seeking behavior, i.e. inescapable novelty-induced locomotor activity (NILA), novelty-induced place preference and novel object exploration, in rats subjected to acute ghrelin receptor (growth hormone secretagogue receptor; GHSR) stimulation or blockade. Furthermore we assessed the possible association between polymorphisms in the genes encoding ghrelin and GHSR and novelty seeking behavior in humans. The rodent studies indicate an important role for ghrelin in a wide range of novelty seeking behaviors. Ghrelin-injected rats exhibited a higher preference for a novel environment and increased novel object exploration. Conversely, those with GHSR blockade drastically reduced their preference for a novel environment and displayed decreased NILA. Importantly, the mesolimbic ventral tegmental area selective GHSR blockade was sufficient to reduce the NILA response indicating that the mesolimbic GHSRs might play an important role in the observed novelty responses. Moreover, in untreated animals, a striking positive correlation between NILA and sucrose reward behavior was detected. Two GHSR single nucleotide polymorphisms (SNPs), rs2948694 and rs495225, were significantly associated with the personality trait novelty seeking, as assessed using the Temperament and Character Inventory (TCI), in human subjects. This study provides the first evidence for a role of ghrelin in novelty seeking behavior in animals and humans, and also points to an association between food reward and novelty seeking in rodents.
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Affiliation(s)
- Caroline Hansson
- Department of Physiology/Endocrinology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
- Department of Clinical and Molecular Medicine, Institute of Medicine, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
| | - Rozita H. Shirazi
- Department of Physiology/Endocrinology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
| | - Jakob Näslund
- Department of Pharmacology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
| | - Heike Vogel
- Department of Physiology/Endocrinology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
| | - Corinna Neuber
- Department of Clinical and Molecular Medicine, Institute of Medicine, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
| | - Göran Holm
- Department of Metabolism and Cardiovascular Disease, Institute of Medicine, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
| | - Henrik Anckarsäter
- Department of Psychiatry and Neurochemistry, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
| | - Suzanne L. Dickson
- Department of Physiology/Endocrinology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
| | - Elias Eriksson
- Department of Pharmacology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
| | - Karolina P. Skibicka
- Department of Physiology/Endocrinology, Institute of Neuroscience and Physiology, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
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Clifford PS, Rodriguez J, Schul D, Hughes S, Kniffin T, Hart N, Eitan S, Brunel L, Fehrentz JA, Martinez J, Wellman PJ. Attenuation of cocaine-induced locomotor sensitization in rats sustaining genetic or pharmacologic antagonism of ghrelin receptors. Addict Biol 2012; 17:956-63. [PMID: 21790898 DOI: 10.1111/j.1369-1600.2011.00339.x] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Systemic infusions of the orexigenic peptide ghrelin (GHR) increase dopamine levels within the nucleus accumbens and augment cocaine-stimulated locomotion and conditioned place preference in rats; observations that suggest an important role for GHR and GHR receptors (GHR-Rs) in drug reinforcement. In the present studies, we examined the development of cocaine locomotor sensitization in rats, sustaining either pharmacologic antagonism or genetic ablation of GHR-Rs. In a pharmacologic study, adult male rats were injected (i.p.) with either 0, 3 or 6 mg/kg JMV 2959 (a GHR-R1 receptor antagonist), and 20 minutes later, with either vehicle or 10 mg/kg cocaine HCl on each of 7 consecutive days. Rats pretreated with JMV 2959 showed significantly attenuated cocaine-induced hyperlocomotion. In a second study, adult wild-type (WT) or mutant rats sustaining ENU-induced knockout of GHR-R [GHR-R ((-/-) )] received daily injections (i.p.) of vehicle (0.9% saline) or 10.0 mg/kg cocaine HCl for 14 successive days. GHR-R null rats treated repeatedly with cocaine showed diminished development of cocaine locomotor sensitization relative to WT rats treated with cocaine. To verify the lack of GHR-R function in the GHR-R ((-/-) ) rats, a separate feeding experiment was conducted in which WT rats, but not GHR-R ((-/-) ) rats, were noted to eat more after a systemic injection of 15 nmol GHR than after vehicle. These results suggest that GHR-R activity is required for the induction of locomotor sensitization to cocaine and complement an emerging literature implicating central GHR systems in drug reward. GHR is an orexigenic gut peptide that is transported across the blood-brain barrier and interacts with GHR-Rs located on ventral tegmental dopamine neurons.
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Affiliation(s)
- P Shane Clifford
- Department of Psychology, Behavioral Neuroscience Program, Texas A&M University, College Station, TX 77843-4235, USA
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Wellman PJ, Clifford PS, Rodriguez JA, Hughes S, Di Francesco C, Melotto S, Tessari M, Corsi M, Bifone A, Gozzi A. Brain reinforcement system function is ghrelin dependent: studies in the rat using pharmacological fMRI and intracranial self-stimulation. Addict Biol 2012; 17:908-19. [PMID: 22017465 DOI: 10.1111/j.1369-1600.2011.00392.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Ghrelin (GHR) is an orexigenic gut peptide that interacts with brain ghrelin receptors (GHR-Rs) to promote food intake. Recent research suggests that GHR acts as a modulator of motivated behavior, suggesting a direct influence of GHR on brain reinforcement circuits. In the present studies, we investigated the role of GHR and GHR-Rs in brain reinforcement function. Pharmacological magnetic resonance imaging was used to spatially resolve the functional activation produced by systemic administration of an orexigenic GHR dose. The imaging data revealed a focal activation of a network of subcortical structures that comprise brain reinforcement circuits-ventral tegmental area, lateral hypothalamus and nucleus accumbens. We next analyzed whether brain reinforcement circuits require functional GHR-Rs. To this purpose, wild-type (WT) or mutant rats sustaining N-ethyl-N-nitrosourea-induced knockout of GHR-Rs (GHR-R null rats) were implanted with stimulating electrodes aimed at the lateral hypothalamus, shaped to respond for intracranial self-stimulation (ICSS) and then tested using a rate-frequency procedure to examine ICSS response patterns. WT rats were readily shaped using stimulation intensities of 75 µA, whereas GHR-R null rats required 300 µA for ICSS shaping. No differences in rate-frequency curves were noted for WT rats at 75 µA and GHR-R null rats at 300 µA. When current intensity was lowered to 100 µA, GHR-R null rats did not respond for ICSS. Taken collectively, these data suggest that systemic GHR can activate mesolimbic dopaminergic areas, and highlight a facilitative role of GHR-Rs on the activity of brain reinforcement systems.
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Affiliation(s)
- Paul J Wellman
- Behavioral Neuroscience Program, Department of Psychology, Texas A&M University, College Station, TX 77843-4235, USA.
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Ma X, Lin Y, Lin L, Qin G, Pereira FA, Haymond MW, Butte NF, Sun Y. Ablation of ghrelin receptor in leptin-deficient ob/ob mice has paradoxical effects on glucose homeostasis when compared with ablation of ghrelin in ob/ob mice. Am J Physiol Endocrinol Metab 2012; 303:E422-31. [PMID: 22669248 PMCID: PMC3423126 DOI: 10.1152/ajpendo.00576.2011] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The orexigenic hormone ghrelin is important in diabetes because it has an inhibitory effect on insulin secretion. Ghrelin ablation in leptin-deficient ob/ob (Ghrelin(-/-):ob/ob) mice increases insulin secretion and improves hyperglycemia. The physiologically relevant ghrelin receptor is the growth hormone secretagogue receptor (GHS-R), and GHS-R antagonists are thought to be an effective strategy for treating diabetes. However, since some of ghrelin's effects are independent of GHS-R, we have utilized genetic approaches to determine whether ghrelin's effect on insulin secretion is mediated through GHS-R and whether GHS-R antagonism indeed inhibits insulin secretion. We investigated the effects of GHS-R on glucose homeostasis in Ghsr-ablated ob/ob mice (Ghsr(-/-):ob/ob). Ghsr ablation did not rescue the hyperphagia, obesity, or insulin resistance of ob/ob mice. Surprisingly, Ghsr ablation worsened the hyperglycemia, decreased insulin, and impaired glucose tolerance. Consistently, Ghsr ablation in ob/ob mice upregulated negative β-cell regulators (such as UCP-2, SREBP-1c, ChREBP, and MIF-1) and downregulated positive β-cell regulators (such as HIF-1α, FGF-21, and PDX-1) in whole pancreas; this suggests that Ghsr ablation impairs pancreatic β-cell function in leptin deficiency. Of note, Ghsr ablation in ob/ob mice did not affect the islet size; the average islet size of Ghsr(-/-):ob/ob mice is similar to that of ob/ob mice. In summary, because Ghsr ablation in leptin deficiency impairs insulin secretion and worsens hyperglycemia, this suggests that GHS-R antagonists may actually aggravate diabetes under certain conditions. The paradoxical effects of ghrelin ablation and Ghsr ablation in ob/ob mice highlight the complexity of the ghrelin-signaling pathway.
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Affiliation(s)
- Xiaojun Ma
- US Department of Agriculture/Agricultural Research Service Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA
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Abstract
Improvement of glucose metabolism after bariatric surgery appears to be from the composite effect of the alterations in multiple circulating gut hormone concentrations. However, their individual effect on glucose metabolism during different conditions is not clear. The objective of this study was to determine whether ghrelin has an impact on glycogenolysis, gluconeogenesis, and insulin sensitivity (using a mice model). Rate of appearance of glucose, glycogenolysis, and gluconeogenesis were measured in wild-type (WT), ghrelin knockout (ghrelin(-/-)), and growth hormone secretagogue receptor knockout (Ghsr(-/-)) mice in the postabsorptive state. The physiological nature of the fasting condition was ascertained by a short-term fast commenced immediately at the end of the dark cycle. Concentrations of glucose and insulin were measured, and insulin resistance and hepatic insulin sensitivity were calculated. Glucose concentrations were not different among the groups during the food-deprived period. However, plasma insulin concentrations were lower in the ghrelin(-/-) and Ghsr(-/-) than WT mice. The rates of gluconeogenesis, glycogenolysis, and indexes of insulin sensitivity were higher in the ghrelin(-/-) and Ghsr(-/-) than WT mice during the postabsorptive state. Insulin receptor substrate 1 and glucose transporter 2 gene expressions in hepatic tissues of the ghrelin(-/-) and Ghsr(-/-) were higher compared with that in WT mice. This study demonstrates that gluconeogenesis and glycogenolysis are increased and insulin sensitivity is improved by the ablation of the ghrelin or growth hormone secretagogue receptor in mice.
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Affiliation(s)
- Shaji K Chacko
- Department of Pediatrics, Baylor College of Medicine Children’s Nutrition Research Center, United States Department of Agriculture/Agricultural Research Service, Houston, TX, USA
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Shepperd E, Peng C, Unniappan S. Ghrelinergic system in fish ovaries and ghrelin inhibition of germinal vesicle breakdown in zebrafish oocytes. Gen Comp Endocrinol 2012; 176:426-31. [PMID: 22342459 DOI: 10.1016/j.ygcen.2012.01.014] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2011] [Revised: 01/20/2012] [Accepted: 01/22/2012] [Indexed: 01/28/2023]
Abstract
Ghrelin, the only known orexigenic gut hormone has been proposed to integrate energy balance and reproduction in mammals. There is a large set of data available on the orexigenic and LH stimulatory roles of ghrelin in fish. Ghrelin and ghrelin receptor mRNAs are expressed in the gonads of several fishes. However, the direct roles of ghrelin on fish gonads remain unclear. Our objective was to identify the ghrelinergic system in fish ovaries, at the protein level in the cross sections of paraffin fixed ovaries, and test the direct effects of ghrelin on oocyte maturation. Both ghrelin and ghrelin receptor like immunoreactivity was detected in the follicle cells in the cross section of goldfish and zebrafish ovaries. This agrees with the mRNA expression data and further confirms the presence of the ghrelinergic system in fish ovaries. We found that native ghrelin at 10, 50 and 100 ng/mL concentrations inhibited both basal and maturation-inducing hormone stimulated stage IV germinal vesicle breakdown (GVBD) of zebrafish oocyte maturation in vitro. This result indicates that ghrelin acts directly on zebrafish follicles. When zebrafish follicles were co-incubated with ghrelin and a well-characterized ghrelin receptor antagonist, D-lys(3)-GHRP-6, the inhibitory effects of ghrelin on stage IV GVBD was abolished. This result indicates that ghrelin inhibits stage IV GVBD via its receptor(s). Collectively, our results for the first time indicate a direct role for ghrelin in the ovarian physiology of fish.
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Affiliation(s)
- Erin Shepperd
- Laboratory of Integrative Neuroendocrinology, Department of Biology, York University, Toronto, Ontario, Canada M3J 1P3
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31
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Rediger A, Piechowski CL, Habegger K, Grüters A, Krude H, Tschöp MH, Kleinau G, Biebermann H. MC4R dimerization in the paraventricular nucleus and GHSR/MC3R heterodimerization in the arcuate nucleus: is there relevance for body weight regulation? Neuroendocrinology 2012; 95:277-88. [PMID: 22327910 DOI: 10.1159/000334903] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/23/2011] [Accepted: 11/06/2011] [Indexed: 01/21/2023]
Abstract
The worldwide obesity epidemic is increasing, yet at this time, no long-acting and specific pharmaceutical therapies are available. Peripheral hormonal signals communicate metabolic status to the hypothalamus by activating their corresponding receptors in the arcuate nucleus (ARC). In this brain region, a variety of G protein-coupled receptors (GPCRs) are expressed that are potentially involved in weight regulation, but so far, the detailed function of most hypothalamic GPCRs is only partially understood. An important and underappreciated feature of GPCRs is the capacity for regulation via di- and heterodimerization. Increasing evidence implicates that heterodimerization of GPCRs results in profound functional consequences. Recently, we could demonstrate that interaction of the melanocortin 3 receptor (MC3R) and the growth hormone secretagogue receptor (GHSR)-1a results in a modulation of function in both receptors. Although the physiological role of GPCR-GPCR interaction in the hypothalamus is yet to be elucidated, this concept promises new avenues for investigation and understanding of hypothalamic functions dependent on GPCR signaling. Since GPCRs are important targets for drugs to combat many diseases, identification of heterodimers may be a prerequisite for highly specific drugs. Therefore, a detailed understanding of the mechanisms and their involvement in weight regulation is necessary. Fundamental to this understanding is the interplay of GPCR-GPCR in the hypothalamic nuclei in energy metabolism. In this review, we summarize the current knowledge on melanocortin receptors and GHSR-1a in hypothalamic weight regulation, especially as they pertain to possible drug targets. Furthermore, we include available evidence for the participation and significance of GPCR dimerization.
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MESH Headings
- Animals
- Appetite Regulation/physiology
- Arcuate Nucleus of Hypothalamus/anatomy & histology
- Arcuate Nucleus of Hypothalamus/metabolism
- Arcuate Nucleus of Hypothalamus/physiology
- Body Weight/physiology
- Humans
- Models, Biological
- Paraventricular Hypothalamic Nucleus/anatomy & histology
- Paraventricular Hypothalamic Nucleus/metabolism
- Paraventricular Hypothalamic Nucleus/physiology
- Protein Multimerization/physiology
- Receptor, Melanocortin, Type 3/metabolism
- Receptor, Melanocortin, Type 3/physiology
- Receptor, Melanocortin, Type 4/metabolism
- Receptor, Melanocortin, Type 4/physiology
- Receptors, Ghrelin/metabolism
- Receptors, Ghrelin/physiology
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Affiliation(s)
- Anne Rediger
- Institute of Experimental Pediatric Endocrinology, Charité Universitätsmedizin Berlin, Humboldt University, Berlin, Germany
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32
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Muccioli G, Lorenzi T, Lorenzi M, Ghè C, Arnoletti E, Raso GM, Castellucci M, Gualillo O, Meli R. Beyond the metabolic role of ghrelin: a new player in the regulation of reproductive function. Peptides 2011; 32:2514-21. [PMID: 22074955 DOI: 10.1016/j.peptides.2011.10.020] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/31/2011] [Revised: 10/23/2011] [Accepted: 10/23/2011] [Indexed: 11/30/2022]
Abstract
Ghrelin is a gastric peptide, discovered by Kojima et al. (1999) [55] as a result of the search for an endogenous ligand interacting with the "orphan receptor" GHS-R1a (growth hormone secretagogue receptor type 1a). Ghrelin is composed of 28 aminoacids and is produced mostly by specific cells of the stomach, by the hypothalamus and hypophysis, even if its presence, as well as that of its receptors, has been demonstrated in many other tissues, not least in gonads. Ghrelin potently stimulates GH release and participates in the regulation of energy homeostasis, increasing food intake, decreasing energy output and exerting a lipogenetic effect. Furthermore, ghrelin influences the secretion and motility of the gastrointestinal tract, especially of the stomach, and, above all, profoundly affects pancreatic functions. Despite of these previously envisaged activities, it has recently been hypothesized that ghrelin regulates several aspects of reproductive physiology and pathology. In conclusion, ghrelin not only cooperates with other neuroendocrine factors, such as leptin, in the modulation of energy homeostasis, but also has a crucial role in the regulation of the hypothalamic-pituitary gonadal axis. In the current review we summarize the main targets of this gastric peptide, especially focusing on the reproductive system.
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Affiliation(s)
- Giampiero Muccioli
- Department of Drug Science and Technology, Division of Medical Pharmacology, University of Torino, Via P. Giuria 13, 10125 Torino, Italy
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33
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Zhi X, Wei J. [Progress in the research of ghrelin and reproductive system]. Sheng Li Ke Xue Jin Zhan 2011; 42:307-310. [PMID: 22066426] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
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Verhulst PJ, Lintermans A, Janssen S, Loeckx D, Himmelreich U, Buyse J, Tack J, Depoortere I. GPR39, a receptor of the ghrelin receptor family, plays a role in the regulation of glucose homeostasis in a mouse model of early onset diet-induced obesity. J Neuroendocrinol 2011; 23:490-500. [PMID: 21470317 DOI: 10.1111/j.1365-2826.2011.02132.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
GPR39, which may function as a Zn(2+) sensor, is a member of the G protein-coupled receptor family that also includes the receptor for the hunger hormone ghrelin. The down-regulation of GPR39 mRNA in adipose tissue of obese type 2 diabetic patients suggests that GPR39 may contribute to the pathogenesis of the disease. The present study aimed to investigate the role of GPR39 in the regulation of energy balance and glucose homeostasis in wild-type (GPR39(+/+) ) and GPR39 knockout mice (GPR39(-/-) ) with obesity-related type 2 diabetes. GPR39 mRNA levels in adipose tissue of fasted GPR39(+/+) mice fed a high-fat diet (HFD) for 30 weeks were reduced and correlated positively with blood glucose levels. Body weight, fat percentage and energy intake were increased in the HFD group but did not differ between both genotypes. Within the HFD group, blood glucose levels were lower in GPR39(-/-) than in GPR39(+/+) mice, despite significant reductions in prandial plasma insulin levels. The latter may not be a result of changes in β-cell hyperplasia because immunohistochemical staining of pancreata of mice on a HFD showed no differences between genotypes. The lower blood glucose levels may involve alterations in insulin sensitivity as revealed by glucose tolerance tests and respiratory quotient measurements that showed a preference of obese GPR39(-/-) mice for the use of carbohydrates as metabolic fuel. The increase in plasma ghrelin levels in GPR39(-/-) mice fed a HFD may contribute to the alterations in glucose homeostasis, whereas changes in gastric emptying or intestinal Zn(2+) absorption are not involved. The results obtained in the present study suggest that GPR39 plays a role in the pathogenesis of obesity-related type 2 diabetes by affecting the regulation of glucose homeostasis.
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MESH Headings
- Age of Onset
- Animals
- Diabetes Mellitus, Type 2/genetics
- Diabetes Mellitus, Type 2/metabolism
- Diet/adverse effects
- Diet, Atherogenic
- Disease Models, Animal
- Genetic Predisposition to Disease
- Glucose/metabolism
- Homeostasis/genetics
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Multigene Family/physiology
- Obesity/epidemiology
- Obesity/etiology
- Obesity/genetics
- Obesity/metabolism
- Receptors, G-Protein-Coupled/genetics
- Receptors, G-Protein-Coupled/metabolism
- Receptors, G-Protein-Coupled/physiology
- Receptors, Ghrelin/genetics
- Receptors, Ghrelin/physiology
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Affiliation(s)
- P J Verhulst
- Department of Pathophysiology, Translational Research Center for Gastrointestinal Disorders, Catholic University of Leuven, Leuven, Belgium
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35
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Abstract
When a child is not following the normal, predicted growth curve, an evaluation for underlying illnesses and central nervous system abnormalities is required and, appropriate consideration should be given to genetic defects causing GH deficiency (GHD). Because Insulin-like-Growth Factor-I (IGF-I) plays a pivotal role, GHD could also be considered as a form of IGF-I deficiency (IGFD). Although IGFD can develop at any level of the GHRH-GH-IGF axis, a differentiation should be made between GHD (absent to low GH in circulation) and IGFD (normal to high GH in circulation). The main focus of this review is on the GH-gene, the various gene alterations and their possible impact on the pituitary gland. However, although transcription factors regulating the pituitary gland development may cause multiple pituitary hormone deficiency they may present initially as GHD. These defects are discussed in various different chapters within this book, whereas, the impact of alterations of the GHRH-, GHRH-receptor- --as well as the GH-receptor (GHR) gene--will be discussed here.
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Affiliation(s)
- Primus-E Mullis
- Division of Paediatric Endocrinology, Diabetology & Metabolism, University Children's Hospital, Inselspital, Bern, Switzerland.
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36
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Affiliation(s)
- Christian Meyer
- Department of Endocrinology, Carl T. Hayden VA Medical Center, Phoenix, Arizona, USA.
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37
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Ceranowicz D, Warzecha Z, Dembinski A, Ceranowicz P, Cieszkowski J, Kusnierz-Cabala B, Tomaszewska R, Kuwahara A, Kato I. Role of hormonal axis, growth hormone - IGF-1, in the therapeutic effect of ghrelin in the course of cerulein-induced acute pancreatitis. J Physiol Pharmacol 2010; 61:599-606. [PMID: 21081804] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Received: 07/26/2010] [Accepted: 09/24/2010] [Indexed: 05/30/2023]
Abstract
Ghrelin is a ligand for growth hormone secretagogue receptor and stimulates release of growth hormone (GH). Recent studies have shown that treatment with ghrelin exhibits protective and therapeutic effect in the course of experimental pancreatitis. The aim of present study was to examine the role of GH and insulin-like growth factor-1 (IGF-1) in these effects. Acute pancreatitis was induced by cerulein. Study was performed on pituitary-intact hypophysectomized rats. Ghrelin was administered twice a day at the dose of 8 nmol/kg/dose. IGF-1 was given twice a day at the dose of 20 nmol/kg/dose. The severity of acute pancreatitis was assessed 0 h or 1, 2, 3, 5 and 10 days after the last dose of cerulein. Administration of cerulein led to the development of acute edematous pancreatitis. In pituitary-intact rats, treatment with ghrelin reduced biochemical indexes of the severity of acute pancreatitis and morphological signs of pancreatic damage, leading to faster regeneration of the pancreas reduction in serum concentration of pro-inflammatory interleukin-1β and decrease in serum activity of amylase and lipase. These effects were accompanied with an improvement of pancreatic blood flow and an increase in pancreatic DNA synthesis. Hypophysectomy delayed the healing of the pancreas and abolished the therapeutic effect of ghrelin. In hypophysectomized rats with pancreatitis, treatment with IGF-1 exhibits therapeutic effect similar to that observed in ghrelin-treated rats with the intact pituitary. We conclude that therapeutic effect of ghrelin in cerulein-induced pancreatitis is indirect and depends on the release of GH and IGF-1.
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Affiliation(s)
- D Ceranowicz
- Department of Physiology, Jagiellonian University Medical College, Cracow, Poland
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38
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Sun Q, Ma Y, Zhang L, Zhao YF, Zang WJ, Chen C. Effects of GH secretagogues on contractility and Ca2+ homeostasis of isolated adult rat ventricular myocytes. Endocrinology 2010; 151:4446-54. [PMID: 20610573 DOI: 10.1210/en.2009-1432] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Ghrelin and its synthetic analogue hexarelin are specific ligands of GH secretagogue receptor (GHS-R) and induce a variety of cardiovascular protective and cardiac positive inotropic effects. The signaling system underlying immediate effects of both GHSs in cardiomyocytes remains undefined. In the present study, we investigated the immediate effects of GHSs on isolated ventricular myocyte shortening, intracellular Ca(2+) ([Ca(2+)](i)) transients, and the L-type Ca(2+) current (I(Ca,L)). Putative intracellular signalling cascades were studied with specific receptor and signalling blockers. In fresh isolated adult Wistar rat ventricular myocytes, GHSs produced a positive inotropic effect in a concentration-dependent manner and increased the amplitude of [Ca(2+)](i) transients and the I(Ca,L). The positive inotropic response was abolished by the GHS-R1a antagonist [D-Lys(3)]-GH-releasing peptide-6 (10 microm). GHS-induced increase in the I(Ca,L) was abolished by [D-Lys(3)]-GH-releasing peptide-6 and protein kinase C inhibitor, chelerythrine chloride (5 microm), but not by protein kinase A inhibitor, KT 5720 (10 microm). We conclude that hexarelin and ghrelin increase the I(Ca,L), through GHS-R1a receptor and protein kinase C signalling cascade, which contribute to its direct positive inotropic effect on cardiomyocytes.
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Affiliation(s)
- Qiang Sun
- Department of Pharmacology, School of Medicine, Xi'an Jiaotong University, Xi'an 710061, China
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Delhanty PJD, Sun Y, Visser JA, van Kerkwijk A, Huisman M, van Ijcken WFJ, Swagemakers S, Smith RG, Themmen APN, van der Lely AJ. Unacylated ghrelin rapidly modulates lipogenic and insulin signaling pathway gene expression in metabolically active tissues of GHSR deleted mice. PLoS One 2010; 5:e11749. [PMID: 20668691 PMCID: PMC2909919 DOI: 10.1371/journal.pone.0011749] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2010] [Accepted: 06/12/2010] [Indexed: 12/25/2022] Open
Abstract
Background There is increasing evidence that unacylated ghrelin (UAG) improves insulin sensitivity and glucose homeostasis; however, the mechanism for this activity is not fully understood since a UAG receptor has not been discovered. Methodology/Principal Findings To assess potential mechanisms of UAG action in vivo, we examined rapid effects of UAG on genome-wide expression patterns in fat, muscle and liver of growth hormone secretagogue receptor (GHSR)-ablated mice using microarrays. Expression data were analyzed using Ingenuity Pathways Analysis and Gene Set Enrichment Analysis. Regulation of subsets of these genes was verified by quantitative PCR in an independent experiment. UAG acutely regulated clusters of genes involved in glucose and lipid metabolism in all three tissues, consistent with enhancement of insulin sensitivity. Conclusions/Significance Fat, muscle and liver are central to the control of lipid and glucose homeostasis. UAG rapidly modulates the expression of metabolically important genes in these tissues in GHSR-deleted mice indicating a direct, GHSR-independent, action of UAG to improve insulin sensitivity and metabolic profile.
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Abstract
Ghrelin is an orexigenic peptide hormone secreted into the systemic circulation predominantly by the X/A-like cells in the mucosa of the stomach. In addiction to central effects on food intake and growth hormone release, ghrelin has also important vascular and metabolic actions. Our laboratory has shown that administration of exogenous ghrelin acutely improves endothelial function by increasing nitric oxide bioavailability and normalizing the alterate balance between endothelin 1/nitric oxide (ET-1/NO) within the vasculature of individuals with metabolic syndrome. Additionally, in endothelial cell cultures, it has been shown that ghrelin directly stimulates NO production using a signaling pathway that involves GHSR-1a, PI 3-kinase, Akt, and eNOS. Other cardiovascular effects of ghrelin include lowering of peripheral resistance, improvement of contractility and cardiac output. In addition ghrelin plays a significant role in the regulation of glucose homeostasis, lipid profiles and body composition. Importantly, ghrelin has antinflammatory and antiapoptotic effects both in vivo and in vitro. This review focuses on the physiological roles of ghrelin in regulating metabolic and endothelial function and on the potential of ghrelin as the therapeutic target to treat metabolic and cardiovascular disorders.
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Affiliation(s)
- Manfredi Tesauro
- Department of Internal Medicine, University of Rome Tor Vergata, Viale Oxford 81, 00133 Rome, Italy.
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Chen CY, Fujimiya M, Laviano A, Chang FY, Lin HC, Lee SD. Modulation of ingestive behavior and gastrointestinal motility by ghrelin in diabetic animals and humans. J Chin Med Assoc 2010; 73:225-9. [PMID: 20685586 DOI: 10.1016/s1726-4901(10)70048-4] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/03/2010] [Accepted: 04/16/2010] [Indexed: 02/07/2023] Open
Abstract
Acyl ghrelin, a 28-amino acid peptide hormone, is the endogenous cognate ligand for the growth hormone secretagogue receptor. Ghrelin is involved in stimulating growth hormone release, eliciting feeding behavior, inducing adiposity and stimulating gastrointestinal motility. Ghrelin is unique for its post-translational modification of O-n-octanoylation at serine 3 through ghrelin O-acyltransferase, and is the only peripheral signal to enhance food intake. Plasma ghrelin levels manifest "biphasic changes" in diabetes mellitus (DM). In the early stage of DM, the stomach significantly increases the secretion of ghrelin into the plasma, and elevated plasma ghrelin levels are correlated with diabetic hyperphagic feeding and accelerated gastrointestinal motility. In the late stage of DM, plasma ghrelin levels may be lower, which might be linked with anorexia/muscle wasting, delayed gastrointestinal transit, and even gastroparesis. Therefore, the unique ghrelin system may be the most important player compared to the other hindgut hormones participating in the "entero-insular axis". Further studies using either knockdown or knockout of ghrelin gene products and ghrelin O-acyltransferase may unravel the pathogenesis of DM, and show benefits in combating this disease and metabolic syndrome.
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Affiliation(s)
- Chih-Yen Chen
- Division of Gastroenterology, Department of Medicine, Taipei Veterans General Hospital, 201, Section 2, Shih-Pai Road, Taipei 112, Taiwan, R.O.C.
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Wan JJ, Cheng B, Wang YF, Mei CL, Liu W, Ke L, He P. [Ghrelin down-regulates ACAT-1 in THP-1 derived foam cells via growth hormone secretagogue receptor-dependent pathway]. Zhonghua Xin Xue Guan Bing Za Zhi 2009; 37:1030-1034. [PMID: 20137333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
OBJECTIVE To investigate the effects of Ghrelin on the expression of acyl coenzyme A:cholesterol acyltransferases-1 (ACAT-1) in THP-1 derived foam cells. METHODS The human monocytic leukemia cell line (THP-1) was chosen in our study. The differentiation of THP-1 cells into macrophages was induced by phorbol 12-myristate 13-acetate. Macrophages were then incubated with oxidized LDL (ox-LDL) to generate foam cells. Ghrelin and [D-Lys3]-GHRP-6, the special antagonist of growth hormone secretagogue receptor (GHS-R), were treated during foam cells formation. The ACAT-1 protein and mRNA levels were detected by Western blot and RT-PCR. The effect of variance of cholesterol content was measured by zymochemistry via-fluorospectrophotometer. RESULTS Ghrelin reduced the content of cholesterol ester in foam cells obviously. ACAT-1 protein and mRNA levels were also decreased. The antagonist of GHS-R inhibited the effects of Ghrelin on ACAT-1 expression in dose-dependent manner. The ACAT-1 mRNA levels of the GHS-R specific antagonist groups (10(-5), 5 x 10(-5), 10(-4) mol/L) were 1.14 +/- 0.04, 1.58 +/- 0.03, 2.40 +/- 0.16, significantly higher than that of the Ghrelin group (0.89 +/- 0.05). And the protein expressions were 1.25 +/- 0.09, 1.77 +/- 0.11, 2.30 +/- 0.09, also higher than that of the Ghrelin group (0.86 +/- 0.08). CONCLUSIONS Ghrelin might interfere atherosclerosis by down-regulating the expression of ACAT-1 via GHS-R pathway.
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Affiliation(s)
- Jing-Jing Wan
- Department of Geriatrics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China
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Johnson AW, Canter R, Gallagher M, Holland PC. Assessing the role of the growth hormone secretagogue receptor in motivational learning and food intake. Behav Neurosci 2009; 123:1058-65. [PMID: 19824771 PMCID: PMC3325544 DOI: 10.1037/a0016808] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The orexigenic neuropeptide ghrelin is an endogeneous ligand for the growth hormone secretagogue receptor (GHS-R). This orexigen is expressed in both the periphery and in the central system, including portions of mesolimbic dopaminergic circuitry that play a role in affective behaviors. Here we examined pharmacological antagonism of GHS-R in motivational incentive learning, as reflected in Pavlovian-to-instrumental transfer (PIT). Furthermore, it is currently unclear whether the previous effects of ghrelin on food intake are mediated by pre- and/or postingestive influences on ingestive behavior. Thus, the authors also conducted detailed analyses of the temporal dynamics of sucrose licking. Mice received low (50 nmol), moderate (100 nmol), and high (200 nmol) intraperitoneal injections of the GHS-R antagonist GHRP-6 [D-Lys3] prior to subsequent transfer and sucrose consumption tests. Low and moderate doses led to an augmentation of PIT, while high dose injections led to generalized performance deficits. In addition, moderate and high doses of the antagonist resulted in reductions in sucrose intake by reducing palatability of the sucrose. These results suggest dissociable functions of GHS-R in its influence over motivational learning and ingestive behavior.
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Affiliation(s)
- Alexander W Johnson
- Neurogenetics and Behavior Center, Department of Psychological and Brain Sciences, Johns Hopkins University, Baltimore, MD, 21218, USA.
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Affiliation(s)
- Inge Depoortere
- Centre for Gastroenterological Research, Gasthuisberg, O&N, box 701, B-3000 Leuven, Belgium.
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Xu G, Li Y, An W, Li S, Guan Y, Wang N, Tang C, Wang X, Zhu Y, Li X, Mulholland MW, Zhang W. Gastric mammalian target of rapamycin signaling regulates ghrelin production and food intake. Endocrinology 2009; 150:3637-44. [PMID: 19406939 PMCID: PMC2717890 DOI: 10.1210/en.2009-0372] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Ghrelin, a gastric hormone, provides a hunger signal to the central nervous system to stimulate food intake. Mammalian target of rapamycin (mTOR) is an intracellular fuel sensor critical for cellular energy homeostasis. Here we showed the reciprocal relationship of gastric mTOR signaling and ghrelin during changes in energy status. mTOR activity was down-regulated, whereas gastric preproghrelin and circulating ghrelin were increased by fasting. In db/db mice, gastric mTOR signaling was enhanced, whereas gastric preproghrelin and circulating ghrelin were decreased. Inhibition of the gastric mTOR signaling by rapamycin stimulated the expression of gastric preproghrelin and ghrelin mRNA and increased plasma ghrelin in both wild-type and db/db mice. Activation of the gastric mTOR signaling by l-leucine decreased the expression of gastric preproghrelin and the level of plasma ghrelin. Overexpression of mTOR attenuated ghrelin promoter activity, whereas inhibition of mTOR activity by overexpression of TSC1 or TSC2 increased its activity. Ghrelin receptor antagonist d-Lys-3-GH-releasing peptide-6 abolished the rapamycin-induced increment in food intake despite that plasma ghrelin remained elevated. mTOR is therefore a gastric fuel sensor whose activity is linked to the regulation of energy intake through ghrelin.
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Affiliation(s)
- Geyang Xu
- Department of Physiology and Pathophysiology, Peking University Health Science Center, Beijing 100083, China
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Liu Y, Yin XH, Qi YF. [Progress in biological effects of cortistatin]. Sheng Li Ke Xue Jin Zhan 2009; 40:219-224. [PMID: 19803425] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Cortistatin, cloned from cerebral cortex in mammal in 1996, is a sort of polypeptide with multiple biological activities and shares high structural homology with somatostatin. It is widely distributed in tissues and organs of human body, such as brain, coronary artery, stomach, kidney, testis, leukocyte and immunological system. A growing evidence indicates that cortistatin exerts many kinds of biological effects including modulating the process of study and memory, inducing sleep, inhibiting inflammation and regulating endocrine metabolism and homeostasis of cardiovascular system. And these effects are mediated by binding somatostatin receptors, grow hormone secretagogues receptor-1a and Mas-related gene X2 receptor. Cortistatin is considered an important factor regulating the balance of body homeostasis.
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Affiliation(s)
- Yue Liu
- Department of Cardiology, the Second Affiliated Hospital of Harbin Medical University, Harbin 150086, China
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Rak A, Szczepankiewicz D, Gregoraszczuk EŁ. Expression of ghrelin receptor, GHSR-1a, and its functional role in the porcine ovarian follicles. Growth Horm IGF Res 2009; 19:68-76. [PMID: 18809347 DOI: 10.1016/j.ghir.2008.08.006] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/08/2008] [Revised: 08/05/2008] [Accepted: 08/12/2008] [Indexed: 11/21/2022]
Abstract
Recently, we reported stimulatory effect of ghrelin alone and in combination with growth hormone (GH) on estradiol secretion, aromatase activity in parallel with inhibitory effect on cell apoptosis. The aim of this study was to analyze the expression of the functional ghrelin receptor (GHS-R type 1a) and the effect of GH on GHSR-1a expression in cultured whole porcine follicles. Using RT-PCR and Western Blots, we demonstrated the presence of GHSR-1a in prepubertal pig ovary and found no influence of GH on either GHSR-1a protein levels or mRNA expression. Additionally, to show if, noted previously by us action of ghrelin on ovarian follicular function is dependent of its binding to GHSR-1a, we used an antagonist of the ghrelin receptor, (D-Lys-3)-GHRP-6. In cultures treated together ghrelin and (D-Lys-3)-GHRP-6, estradiol secretion, aromatase activity and cell proliferation returned to control levels. Inhibitory action on caspase-3 activity was not reversed by a selective antagonist of GHSR-1a. In conclusion, results of the present data clearly showed: (1) the presence of GHSR-1a in prepubertal pig ovary and found no influence of GH on GHSR-1a protein levels and mRNA expression, and (2) ghrelin effect on estradiol secretion, aromatase activity and cell proliferation dependent of its binding to GHSR-1a, while the effect on cellular apoptosis was independent of its binding to GHSR-1a.
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Affiliation(s)
- Agnieszka Rak
- Department of Physiology and Toxicology of Reproduction, Chair of Animal Physiology, Institute of Zoology, Jagiellonian University, Kraków, Poland
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Wang DH, Hu YS, Du JJ, Hu YY, Zhong WD, Qin WJ. Ghrelin stimulates proliferation of human osteoblastic TE85 cells via NO/cGMP signaling pathway. Endocrine 2009; 35:112-7. [PMID: 18953675 DOI: 10.1007/s12020-008-9117-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/28/2008] [Revised: 09/16/2008] [Accepted: 10/10/2008] [Indexed: 12/23/2022]
Abstract
Ghrelin regulates bone formation and osteoblast proliferation, but the detailed signaling pathway for its action on osteoblasts remains unclear. In human osteoblastic TE85 cells, we observed the effects and intracellular signaling pathway of ghrelin on cell proliferation using BrdU incorporation method. Ghrelin, at 10(-10)-10(-8) M concentration, significantly increased BrdU incorporation into TE85 cells. The action of ghrelin was inhibited by D: -Lys3-GHRP-6, a selective antagonist of GHS-R. Nitric oxide (NO) scavenger hemoglobin and the NO synthase inhibitor NAME eliminated the stimulatory action of ghrelin on proliferation, while NO donor SNAP and NO synthase substrate L-AME stimulated proliferation of osteoblastic TE85 cells. The cGMP analogue, 8-Br-cGMP, stimulated TE85 cell proliferation, and ghrelin did not enhance proliferation in the presence of 8-Br-cGMP. Inhibition of cGMP production by the guanylate cyclase inhibitor prevented ghrelin-induced osteoblastic TE85 cell proliferation. In conclusion, ghrelin stimulates proliferation of human osteoblastic TE85 cells via intracellular NO/cGMP signaling pathway.
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Affiliation(s)
- Deng-Hu Wang
- Department of Orthopedics, Xijing Hospital, Fourth Military Medical University, Xi'an, 710032, China
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Abstract
Ghrelin is known to promote neuronal defense and survival against ischemic injury by inhibiting apoptotic processes. In the present study, we investigated the role of prostate apoptosis response-4 (Par-4), a proapoptotic gene the expression of which is increased after ischemic injury, in ghrelin-mediated neuroprotection during middle cerebral artery occlusion (MCAO). Both ghrelin and des-acyl ghrelin protected cortical neurons from ischemic injury. Ghrelin receptor specific antagonist abolished the protective effects of ghrelin, whereas those of des-acyl ghrelin were preserved, suggesting the involvement of a receptor that is distinct from GHS-R1a. The expression of Par-4 was increased by MCAO, which was attenuated by ghrelin and des-acyl ghrelin treatments. Both ghrelin and des-acyl ghrelin increased the Bcl-2/Bax ratio, prevented cytochrome c release, and inhibited caspase-3 activation. Our data indicate that des-acyl ghrelin, as well as ghrelin, protect cortical neurons against ischemic injury through the inhibition of Par-4 expression and apoptotic molecules in mitochondrial pathway.
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Affiliation(s)
- Sunyoung Hwang
- Department of Pharmacology and Medical Research Center for Bioreaction to ROS and Biomedical Science Institute, Kyunghee University School of Medicine, Seoul, Korea
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Peeters TL. Old and new targets for prokinetic drugs: motilin and ghrelin receptors. Eur Rev Med Pharmacol Sci 2008; 12 Suppl 1:136-137. [PMID: 18924456] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Affiliation(s)
- T L Peeters
- Center for Gastroenterological Research, University of Leuven, Leuven, Belgium.
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